Panda Poop Might Help Turn Plants Into Fuel

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The same organisms that make pandas effective at digesting bamboo may help turn plant waste into biofuels, according to researchers.

Photograph by Keren Su, Corbis

Can panda poop help power the greener vehicles of tomorrow? It just might, scientists say, by yielding microbes that efficiently turn plant waste into biofuel—and the research just might help protect pandas at the same time. (See related quiz: "What You Don't Know About Biofuel.")

"We have discovered microbes in panda feces might actually be a solution to the search for sustainable new sources of energy," Mississippi State University biochemist Ashli Brown, who led the study, told attendees at a meeting of the American Chemical Society (ACS) Tuesday. "It's amazing that here we have an endangered species that's almost gone from the planet, yet there's still so much we have yet to learn from it. That underscores the importance of saving endangered and threatened animals."

Biofuels made from corn, soybeans, and other edible crops cause concerns over their potential impact on food supply and prices. Some even argue that such biofuels ultimately may produce even more carbon emissions than petroleum. (See related coverage: "Biofuels at a Crossroads.")

Waste plant material, such as corn cobs and discarded stalks, long has been eyed as a rich, renewable source of biofuel feedstock. But in order for cellulosic biofuel to truly go mainstream, it must be transformed into ethanol efficiently and economically. That's where panda stomachs could give producers a valuable head start. (Vote in poll: "Are Biofuels Worth the Investment?")

"These microbes may be very well suited to break down this biomass," said co-researcher Candace Williams, who originally developed the study several years ago while working on her master's degree. "That's what they are doing in the gut of the panda with all of the bamboo the animal eats."

The Panda's Powerful Gut

Currently, plant waste biofuel processors must break down the tough composition of stalks or stems by cooking them with heat and/or pressure, or by treating them with substances like acids, to produce the simple sugars that they ferment into a final product—processes that can be difficult to scale economically.

Microbes could help make this process faster and cheaper, and the bacteria that dwell within pandas might be especially effective. After all, the tiny organisms can handle the 20 to 40 pounds of bamboo an adult panda eats each day. Pandas eat bamboo almost exclusively, munching for 12 hours out of every 24 each day.

Thanks to fecal contributions from Ya Ya and Le Le, giant pandas at Tennessee's Memphis Zoo, Brown and Williams have identified more than 40 different panda gut microbe species so far.

"We started out with the pandas because of their diet," Williams said. "They are really unique animals in that they are physiologically like a carnivore, but they eat a herbivorous diet. If you're studying these microorganisms that allow the panda to use this cellulose in bamboo for nutrition, you can see how they might be useful for investigating one of the main problems for biofuels—breaking down those lignocellulosic materials to produce sugars."

Pandas also have short digestive tracts for such large animals, and just a single stomach chamber, Williams added. (Cows, in comparison, use four different stomach regions to gradually remove the energy from grass.) "This means their bacteria have to be even more potent at breaking down the material quickly," she said, "making them very efficient and perhaps even more promising for biofuel production."

Pandas eat both the tough stalks and more tender leaves of the bamboo plant, and their many species of gut microbes wax and wane in number with these dietary changes, Williams said. In addition to producing sugars, some microbes in the lab were even able to accumulate lipids, which can produce the fatty acids needed for biofuel production.

Either the gut bacteria themselves, or the enzymes they use to do the work, possibly could be co-opted for cheaper, easier industrial biofuel production processes, the study's authors said. Yeasts, for example, could be genetically engineered to produce the beneficial enzymes and then grown on a large scale.

Fuel From Whisky, Fat, and Algae

Panda poop is just one promising avenue of research into how waste can be transformed more easily into greener energy.

Some projects are already producing fuel from plant waste materials. Earlier this year, Mississippi-based KiOR shipped what it says is the world's first commercial volume of cellulosic diesel fuel, made from pine wood chips. (See related story: "Beyond Ethanol: Drop-In Biofuels Squeeze Gasoline From Plants.") In August, Florida's Indian River BioEnergy Center also began shipping cellulosic ethanol (sourced from wastes, woodchips, cornstalks, and grasses) at commercial scale. The plant's operator, INEOS Bio, said the facility will produce some eight million gallons of ethanol from yard clippings and wood scraps, using hybrid gasification-fermentation technology.

"Electrofuels" researchers are using microorganisms to produce biofuels in the lab without any plants at all by genetically engineering microorganisms to "poop out" chemicals that can burn right in the gas tank. The U.S. Department of Energy helps fund this and similar initiatives out of its Bioenergy Technologies Office.

For the next phase of panda poop research, droppings from another pair of giant pandas, the Toronto Zoo's Er Shun and Da Mao, may soon be added to the microbe investigation.

Brown explained at her ACS presentation that charismatic and endangered pandas like them may benefit from the research as well as biofuel producers. Detailed analysis of their gut microbes could reveal better ways to keep them healthy, because most of the diseases that affect pandas occur in the gut, Brown said.

"Understanding the relationships between the microbes and the pandas, as well as how they get their energy and nutrition, is extremely important from a conservation standpoint," she said, "as fewer than 2,500 giant pandas are left in the wild, and only 200 are in captivity."